Milling operations at subterranean locations involve fluid circulation that is intended to remove cuttings to the surface. Some of these cuttings do not get transported to the surface and settle out on a wellbore support such as a packer or bridge plug that is below. In open hole situations the wellbore can collapse sending debris into the borehole. Over time sand and other debris can settle out on a borehole support and needs to be removed for access to the support or to allow further subterranean operations.
Wellbore cleanup tools have been used to remove such debris. Different styles have developed over time. In a traditional style the motive fluid goes through the center of the tool and out the bottom to fluidize the debris and send the debris laden stream around the outside of the tool where a diverter redirects flow through the tool body. A receptacle collects the debris as the clean fluid passes through a screen and is discharged above the diverter for the trip to the surface.
Another type of tool has a jet stream going downhole outside the tool to drive debris into the lower end of the tool where debris is collected and clean fluid that passes through a screen is returned to the surface outside the tool through ports located near the downhole oriented jet outlets. The jet outlets act as an eductor for pulling in debris laden flow into the lower end of the tool. Some examples of such tools are U.S. Pat. Nos. 6,176,311; 6,607,031; 7,779,901; 7,610,957; 7,472,745; 6,276,452; 5,123,489. Debris catchers with a circulation pattern that takes debris up on the outside of the tool body and routes it into the tool with a diverter are illustrated in U.S. Pat. Nos. 4,924,940; 6,189,617; 6,250,387 and 7,478,687.
The use of centrifugal force to separate components of different densities is illustrated in a product sold by Cavins of Houston, Tex. under the name Sandtrap Downhole Desander for use with electric submersible pump suction lines. U.S. Pat. No. 7,635,430 illustrates the use of a hydro-cyclone on a wellhead. Also relevant to the subterranean debris removal field is SPE 96440; P. Connel and D. B. Houghton; Removal of Debris from Deep Water Wellbore Using Vectored Annulus Cleaning System Reduces Problems and Saves Rig Time. Also relevant to the field of subterranean debris removal are U.S. Pat. Nos. 4,276,931 and 6,978,841.
Current designs of debris removal devices that take in the debris with fluid reverse circulating into the lower end of the tool housing have used a straight shot for the inlet tube coupled with a deflector at the top that can be a cone shape 10 as in FIG. 1 or a flat plate 12 as in FIG. 2. Arrow 14 represents the direction the solids need to go to be collected in the chamber 16 that is disposed around the inlet tube 18. One of the concerns of the FIGS. 1 and 2 designs is that a very long separation chamber that is between the cone 10 or the plate 12 and the outlet 20 is needed to separate the debris from the flowing fluid using gravity and the slowing for fluid velocity that occurs when the stream of debris laden fluid exits the inlet tube 18 and goes into the larger diameter of the housing 22 on the way to the outlet 20. After the outlet 20 there is a screen and what debris that does not fall out into the chamber 16 winds up putting a load on that screen above which impedes circulation and ability to pick up debris in the first place. Increasing the inlet velocity in an effort to entrain more debris into the tube 18 also winds up being counterproductive in the FIGS. 1 and 2 designs as the higher velocity after an exit from the tube 18 also causes higher turbulence and re-entrainment of the debris that would otherwise have been allowed to settle by gravity into the collection chamber 16. FIG. 9 illustrates the known VACS from Baker Hughes, a portion of which is shown in FIGS. 1 and 2. It also shows that the flow from exit 22 goes into a screen 23 and is then educted into a feed stream 25 from the surface. After the eductor exit 27 the flow splits with 29 going to the surface and 31 going to the bottom and into the inlet tube 18.
The present invention seeks to enhance the separation effect and do so in a smaller space and in a manner that can advantageously use higher velocities to enhance the separation. This is principally accomplished by inducing a swirl to the incoming debris laden fluid stream. The inlet tube can have spiral grooves or internal protrusions that impart the spiral pattern to the fluid stream so that the solids by centrifugal force are hurled to the outer periphery on the way to the outlet of the housing and the downstream screen. These and other aspects of the present invention will be more readily apparent to those skilled in the art from a review of the description of the preferred embodiment and the associated drawings while understanding that the full scope of the invention is to be determined from the appended claims.